RE: [Xen-devel] Intercepting memory operations of a guest

["Sina Bahram" <sbahram@xxxxxxxxx>]

Hi Tim,

Thanks for your response.

I'll do some more poking around, and come back with any further questions.

Take care,
Sina
 

-----Original Message-----
From: Tim Deegan [mailto:Tim.Deegan@xxxxxxxxxx] 
Sent: Tuesday, December 09, 2008 5:09 AM
To: Sina Bahram
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Intercepting memory operations of a guest

Hi,

At 11:54 -0500 on 08 Dec (1228737297), Sina Bahram wrote:
> What do you mean by the statement that it won't catch "all changes" but
only
> those seen by the mmu?
 
You might not see changes made before a pagetable is used for the first
time, or after it stops being used.  Potentially you might miss other
changes as well.  But you are guaranteed that if any pagetable state is
ever seen by the hardware, (that is, used in a VA->PA translation) you
will have seen that state first.

> Also, where can I read more about what enabling shadow page tables means
for
> pv guests?

Not much documentation, I'm afraid.  The source code has some comments
in it (xen/arch/x86/mm/shadow/*) and there's always the live-migration
paper for an overview, though implementation details there are quite out
of date:
http://www.cl.cam.ac.uk/research/srg/netos/papers/2005-nsdi-migration.pdf
 
Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]


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